Corrosion of metals and alloys -- Sulfur dioxide test in a humid atmosphere (fixed gas method)

This document specifies a method for assessing the resistance of materials or products to a humid atmosphere containing sulfur dioxide. This method is applicable to testing metals and alloys, metallic and non-organic coatings and organic coatings.

Corrosion des métaux et alliages -- Essai au dioxyde de soufre en atmosphère humide (méthode avec volume fixe de gaz)

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Status
Published
Publication Date
13-May-2019
Current Stage
6060 - International Standard published
Start Date
12-Apr-2019
Completion Date
14-May-2019
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ISO 22479:2019 - Corrosion of metals and alloys -- Sulfur dioxide test in a humid atmosphere (fixed gas method)
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INTERNATIONAL ISO
STANDARD 22479
First edition
2019-05
Corrosion of metals and alloys —
Sulfur dioxide test in a humid
atmosphere (fixed gas method)
Corrosion des métaux et alliages — Essai au dioxyde de soufre en
atmosphère humide (méthode avec volume fixe de gaz)
Reference number
ISO 22479:2019(E)
ISO 2019
---------------------- Page: 1 ----------------------
ISO 22479:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
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Email: copyright@iso.org
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Published in Switzerland
ii © ISO 2019 – All rights reserved
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ISO 22479:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Apparatus ..................................................................................................................................................................................................................... 1

6 Test specimens........................................................................................................................................................................................................ 3

6.1 General ........................................................................................................................................................................................................... 3

6.2 Dimensions ................................................................................................................................................................................................. 3

6.3 Preparation ................................................................................................................................................................................................ 3

6.3.1 Metals and alloys ............................................................................................................................................................. 3

6.3.2 Paints and varnishes ..................................................................................................................................................... 3

6.4 Arrangement of the test specimens ...................................................................................................................................... 4

7 Test conditions ....................................................................................................................................................................................................... 4

7.1 Test cycles .................................................................................................................................................................................................... 4

7.2 Test duration ............................................................................................................................................................................................. 5

8 Procedure..................................................................................................................................................................................................................... 6

8.1 Introduction of water ........................................................................................................................................................................ 6

8.2 Arrangement of the test specimens ...................................................................................................................................... 6

8.3 Introduction of sulfur dioxide .................................................................................................................................................... 6

8.4 Heating the test cabinet................................................................................................................................................................... 6

8.5 Introduction of standard atmosphere ................................................................................................................................ 6

8.6 Replacement of water and sulfur dioxide ........................................................................................................................ 6

8.7 Cleaning of test specimens after test ................................................................................................................................... 6

8.7.1 General...................................................................................................................................................................................... 6

8.7.2 Metals and alloys, metallic and non-organic coating test specimens ................................. 6

8.7.3 Organic coating test specimens ........................................................................................................................... 7

8.8 Performance check .............................................................................................................................................................................. 7

9 Evaluation .................................................................................................................................................................................................................... 7

10 Test report ................................................................................................................................................................................................................... 7

Annex A (informative) Another example of a test cabinet ............................................................................................................. 9

Annex B (informative) Performance check .................................................................................................................................................10

Annex C (informative) Supplemental information .............................................................................................................................12

Bibliography .............................................................................................................................................................................................................................14

© ISO 2019 – All rights reserved iii
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ISO 22479:2019(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso

.org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.

This first edition of ISO 22479 cancels and replaces ISO 3231:1993 and ISO 6988:1985, which have been

combined and technically revised. The main changes compared with the previous edition are as follows:

— the method of generating sulfur dioxide from reagents has been deleted because of the risk of

exposure to toxic chemicals.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved
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ISO 22479:2019(E)
Introduction
A humid atmosphere containing sulfur dioxide induces corrosion of many metals.

The results obtained in this document should not be regarded as a direct guide to the corrosion

resistance of the tested materials in all environments where these materials may be used. Similarly,

performances of different materials in this document should not be taken as a direct guide to the

relative corrosion resistance of these materials in service.

It is appropriate to test only the same corrosion protection systems at the same time in one test

procedure, because an interaction between samples can't be prevented. When testing different

corrosion protection systems with different materials, it should be taken into account that the influence

of sulfur dioxide often can be different.

The term “fixed gas method” means that at the beginning of the test a fixed volume of gas is introduced

into a cabinet of fixed volume.
© ISO 2019 – All rights reserved v
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INTERNATIONAL STANDARD ISO 22479:2019(E)
Corrosion of metals and alloys — Sulfur dioxide test in a
humid atmosphere (fixed gas method)

WARNING — This document does not purport to address all of the safety concerns, if any,

associated with its use. It is the responsibility of the user of this document to establish

appropriate safety and health practices.
1 Scope

This document specifies a method for assessing the resistance of materials or products to a humid

atmosphere containing sulfur dioxide.

This method is applicable to testing metals and alloys, metallic and non-organic coatings and organic

coatings.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 1514, Paints and varnishes — Standard panels for testing
ISO 2808, Paints and varnishes — Determination of film thickness
ISO 8044, Corrosion of metals and alloys — Basic terms and definitions
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 8044 apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle

The test specimens are exposed to a humid atmosphere containing sulfur dioxide. The sulfur dioxide

dissolved by the moisture condenses on the test specimen surface and causes corrosion.

5 Apparatus
5.1 Component protection.

All components in contact with sulfur dioxide in a humid atmosphere shall be made of corrosion

resistant materials, and shall themselves not emit any gas or vapour likely to influence corrosion of the

test specimens.
© ISO 2019 – All rights reserved 1
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ISO 22479:2019(E)
5.2 Test cabinet.

The preferred capacity of the test cabinet is (300 ± 10) l. When agreed between the interested parties,

other capacities may be used. In these cases, the size and/or number of test specimens, the volume of

gas and the quantity of water shall be properly arranged in accordance with the capacity of the test

cabinet.

The upper part of the cabinet shall be designed so that drops of condensed water formed on its surface

do not fall on the test specimens being tested. An inclination of the upper part of the test cabinet of about

12° or more to the horizontal plane provides a suitable safeguard. The test specimens may be placed at

different levels within the cabinet, as long as the solution does not drip from the test specimens or their

supports at one level onto other test specimens placed below.

The temperature in the test cabinet is controlled by heating the floor and lower part of the side walls

of the test cabinet. The temperature shall be measured at least 250 mm from the side walls and at least

150 mm below the upper part (lid).

A gas inlet port shall be less than 50 mm above the water surface. The test cabinet shall be hermetically

leak-tight.

A pressure relief valve shall be placed in or near the upper part of the test cabinet.

The exhaust gas and the released gas from the pressure relief valve shall be treated as appropriate.

NOTE Relevant regulatory limitations can apply.
A drain port shall be provided in the test cabinet.

A typical test cabinet is shown in Figure 1. Another example of test cabinet is shown in Figure A.1.

The test cabinet shall be installed in a room free from dust, draughts, corrosive gas and direct solar

radiation, at a room temperature of (23 ± 5) °C and at a relative humidity of less than 75 %.

Key
1 lid 5 gas inlet port 9 heater
2 test specimens 6 flowmeter 10 drain port
3 specimen supports 7 source of sulfur dioxide 11 pressure relief valve
4 water inside the cabinet 8 water tank 12 temperature measurement
Figure 1 — Typical test cabinet
2 © ISO 2019 – All rights reserved
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ISO 22479:2019(E)
5.3 Source of sulfur dioxide.

The source of sulfur dioxide should be a gas cylinder with a volume concentration of more than 99,9 %. It

shall be fitted with appropriate regulating and measuring apparatus to ensure the supply of the correct

volume of gas. The volume of gas delivered into the test cabinet should be measured by a calibrated

flow meter. Another measuring instrument works with squeezing out a viscous liquid paraffin for the

volume of the gas for 0,2, 1,0 and 2,0 l.

WARNING — Sulfur dioxide (CAS no. 7446-09-5) is toxic, corrosive and irritating. Handling of

sulfur dioxide shall be restricted to skilled personnel or conducted under their control. The

apparatus shall be used and maintained by skilled personnel, not only so that the procedures can

be performed correctly, but also because of the hazards to health and safety that are involved.

5.4 Conditioning of a new cabinet.

In order to minimize the effect from the material of the cabinet by sulfur dioxide, a new cabinet shall

be operated at least one test cycle in accordance with the procedures given in 8.2 to 8.5 without test

specimens. The conditioning shall conform to Table 1, with 2,0 l of sulfur dioxide.

6 Test specimens
6.1 General

The number, type, surface roughness, thickness of coatings, shape and dimensions of test specimens

shall be selected according to the specification for the materials or product being tested. When not

specified, details concerning the test specimens shall be agreed between the interested parties.

6.2 Dimensions
A typical specimen size is 150 mm × 100 mm by 0,75 mm to 1,25 mm thickness.
6.3 Preparation
6.3.1 Metals and alloys

Thoroughly clean the test specimens before testing. The cleaning method depends on the nature of the

surface and the contaminants. Abrasives shall not include the use of any abrasives or solvents that may

attack the surface of the test specimens. Take care that the test specimens are not recontaminated after

cleaning, by excessive or careless handling.

If test specimens are cut from a large coated article, the cutting shall be carried out in such a way that

the coating is not damaged, especially in the area adjacent to the cut. Unless otherwise specified, the

cut edges should be adequately protected by coating with a suitable medium that is stable under the

conditions of test, such as wax or adhesive tape.
6.3.2 Paints and varnishes

Unless otherwise specified or agreed, the test specimens shall be prepared in accordance with ISO 1514

and then coated by the specified method with the product or system under test. The back and edges of

the test specimens should be coated with the product or system under test.
Dry (or cure) and age (if applicable) each coa
...

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